Post on 26-Dec-2015
Kate Fullerton & Deborah Bakshiyev
B9 - Respiration
B.9.1 - Compare aerobic and anaerobic respiration of glucose in terms of oxidation/reduction and energy
released.
Respiration for Chemists
• Respiration is the controlled breakdown of energy-rich substances into usable forms• Ex. Glucose ATP
Glycolysis
• Glucose (C6H12O6) and NAD+ react to form Pyruvate (C3H3O3
-), NADH, H+, and energy
C6H12O6 + 2 NAD+ 2C3H3O3- + 2NADH + 4H+
• Half equations:
C6H12O6 2 C3H3O3- + 6H+ + 5e-
NAD+ + 2H+ + 2e- NADH
Reduction:
Oxidation:
It’s anaerobic!
Aerobic Respiration
This process requires O2 from the air• O2 acts as the oxidizing agent• It is the ultimate terminal electron acceptor and is
reduced to water• Final products are CO2, H2O, and energy• Pyruvate to CO2 and H2O:
C3H3O3- + NADH + 2H+ + 3O2
3CO2 + 3H2O + NAD+
Aerobic RespirationHalf-Equations:
3O2 + 12H+ + 12e- 6H2O
C3H3O3- + 3H2O 3CO2 + 9H+ + 9e-
NADH is also oxidized
Reduction:
Oxidation:
Aerobic RespirationOverall equation (glucose products):
C6H12O6 + 6O2 6CO2 + 6H2O
Glucose is oxidized while oxygen is reducedThis equation should look familiar…
The overall equation is the same as combustionHowever this process is much more complex with
many steps and is controlled by enzymes
Anerobic RespirationWhen no oxygen is present, anerobic
respiration (or fermentation) occursIn humans, pyruvate is converted into lactic
acid (C3H6O3)In yeast, pyruvate is converted into ethanol
and CO2
Anerobic RespirationPyruvate Lactic Acid
C3H3O3- + NADH + 2H+ C3H6O3 + NAD+
Half equations:
C3H3O3- + 3H+ + 2e- C3H6O3
NADH NAD+ + 2H+ + 2e-
• Lactic acid causes your muscles to feel sore• NAD+ is used to reduce more pyruvate (cyclic)
Reduction:
Oxidation:
Anerobic RespirationPyruvate Ethanol and CO2
C3H3O3- + NADH + 2H+ C2H5OH + CO2 + NAD+
Half equations:
C3H3O3- + 3H+ + 2e- C2H5OH + CO2
NADH NAD+ + 2H+ + 2e-
NAD+ is used to reduce more pyruvate (cyclic)
Reduction:
Oxidation:
Anerobic RespirationOverall equations:
Glucose Lactic AcidC6H12O6 2C3H6O3
Glucose EthanolC6H12O6 2C2H5OH + 2CO2
Energy ReleaseAerobic respiration releases about 40% of the
energy in glucoseAnerobic respiration releases about 2% of the
energy in glucose
*This is because aerobic respiration oxidizes glucose more fully than anaerobic respiration*
B.9.2 - Outline the role of copper ions in electron transport and iron
ions in oxygen transport
Role of Copperin electron transport In the electron transport chain at the end of respiration electrons are
passed between proteins in a membrane. – These proteins are called transport carriers
Many of these types of electron transport carriers are cytochromes. – They are proteins that contain a non-protein component called a
prosthetic group– contain iron and copper – reduced by electrons (in the electron chain) • Remember: RIG reduction is gain of electrons!
• Later, they are re-oxidized (continue passing along the electron transport chain)– HEME groups are the receptors of the electrons– The iron in the heme group is oxidized from +2 to +3.
Diagram of the heme structure of cytochromes
Role of Copperin electron transportThe terminal electron carrier in the electron transport
chain is cytochrome oxidase and contains copper as well as Fe. – copper receives the electron • The Cu changes its oxidation state from +1 to +2 as it
is oxidized.• Binds the electron to O 2 forms water
Danger of Cyanide (CN-)CN- binds to the cytochrome oxidase
backs up the electron transport chainslows respiration
Role of Iron in oxygen transport• Hemoglobin
– made of 4 polypeptides• Each polypeptide has its own HEME group
– HEME group = a complex ion! – Each HEME group contains Fe2+
• So, there are 4 Fe2+ in each hemoglobin molecule• In hemoglobin (blood) and myoglobin (muscles) oxygen is transported in a similar
heme structure. – Hydrophobic environment allows oxygen to bind to Fe2+ without oxidizing it (the
Fe stays in the +2 state) So, hemoglobin is described as being oxygenated to oxyhemoglobin rather than
oxidized. • Quick review: there are 4 HEME groups that means there are 4 Fe2+ so, every
hemoglobin can bind to 4 O2
The reversible equation is:– Hb + 4O2 Hb(O2) 4
Danger of Carbon monoxide (CO)• CO binds more tightly to Fe2+ –So you can think that the CO sort of steals
the oxygen’s spot with the Fe2+ • Causes lack of oxygen– If CO is not displaced asphyxiation